1. Field of the Invention
The present invention relates to coaxial connectors, particularly to a coaxial connector that is surface-mounted on a circuit board and can be used in high-frequency signal transmission paths.
2. Description of the Related Art
FIG. 1A shows a conventional coaxial connector 1 that is mounted on a circuit board 10. The coaxial connector 1 comprises a core center conductor 2 disposed at the center, an insulating member 3 surrounding the center conductor 2, and a cylindrical surrounding conductor 4 that surrounds the insulator 3. A lower-end portion 2a of the center conductor 2 protrudes downward beyond the insulating member 3. The surrounding conductor 4 has a flange portion 4a at the lower end.
FIG. 1B shows a portion of the circuit board 10 where the coaxial connector 1 is mounted. The circuit board 10 has a throughhole 11 through which the lower-end portion 2a of the center conductor 2 penetrates. On the upper surface of the circuit board 10, a ring-shaped ground pad 12 is formed about the throughhole 11. On the lower surface, a ring-shaped pad 13 is formed about the throughhole 11.
As shown in FIG. 1C, the coaxial connector 1 is mounted on the circuit board 10 by soldering the periphery of the flange portion 4a to the ground pad 12 with a solder portion 20 and soldering the lower-end portion 2a of the center conductor 2, which penetrates downward through the throughhole 11, to the pad 13 with a solder portion 21.
With the coaxial connector 1 thus mounted on the circuit board 10, a coaxial connector 31 affixed to the end of a coaxial cable 30 is coupled.
In this conventional example, the solder portions 20 and 21 at the two locations of the assembly produce inductance. This inductance could be of such a value that degradation in signal transmission characteristics at the coaxial connector 1 cannot be disregarded in cases involving high-frequency transmission signals of several 10 GHz or above.
Furthermore, the throughhole 11 that needs to be formed in the circuit board 10 for mounting the coaxial connector 1 can cause degradation in signal transmission characteristics that cannot be disregarded when the transmitted signal is on the order of several 10 GHz or above.